The invention relates to an electrical machine, in particular a claw pole generator for motor vehicles, as generically defined by the preamble to the independent claim.
Electrical machines for motor vehicles are known from European Patent EP 0 720 275, for instance. The known electrical machine includes a rotor of the claw pole type, which comprises among other elements a shaft, two pole wheels, an exciter coil, and a pole closure. The pole closure is embodied such, that it closes the interstices of the claw poles of opposite polarity; that no flow is detached on the radially outer, approximately axially oriented edges of the poles and thus prevents the attendant noise production. The claw closure is also embodied such that a substantial portion of its centrifugally acting intrinsic load is transmitted to the claw pole tips via the inside of these tips.
This known electrical machine has the disadvantage, among others, that by the absorption of the centrifugal load of the claw closure via the claw poles, an additional load is exerted on the claw poles in addition to their intrinsic load.
With the electrical machine of the invention as defined by the characteristics of the independent claim, it is possible to transmit the intrinsic centrifugal load of the claw closure to the pole wheels in such a way that the poles and counterpart or opposite poles are not loaded. To that end, it is provided that the pole closure is braced by at least one of its axial end regions, via projections, on the pole roots.
By the provisions recited in the dependent claims, advantageous refinements of and improvements to the characteristics disclosed in the independent claim are obtained.
In the region of the axial end regions, the pole closure has recesses, into which the projections of the pole roots are fitted. This has the advantage that an essentially cylindrical surface of the rotor is thus obtained.
Because the pole wheels are produced by a reshaping process, it is advantageous if the projections are likewise fabricated by reshaping.
In a further feature of the invention, between at least one end region of the pole closure and at least one throat between two pole roots, an opening remains recessed out toward a space radially inside the poles and counterpart poles. This recessing makes a better inflow of an impregnating resin for fixing the exciter coil possible.
So that the air flow will not detach at the transition from the outward-oriented surfaces of the poles and counterpart poles to the pole closure, the transition between the surfaces and counterpart poles of the pole closure and the poles and counterpart poles must be effected in infinitely graduated fashion.
To obtain better intrinsic stiffness of the pole closure, the closure regions of the pole closure are joined together by a ring. A further improvement in the pole closure is obtained by providing that a region between the ring and an end region of the pole closure is closed by a face element.
So that the pole closure between two projections at the pole roots will not be subjected to overly severe bending stress, the face element in a further feature of the invention should be braced on a radially inward-oriented underside of a pole or counterpart pole.